Ischemia/reperfusion injury is a common pathophysiologic process that occurs in acute renal failure, coronary artery disease and cerebrovascular disease. Acute ischemic renal failure, a frequent clinical problem, results in a mortality rate of 4O-6O% and has no accepted treatment. We have reported that an antibody to intercellular adhesion molecule-1 (ICAM- 1) protects against both the functional and histological abnormalities of acute ischemic renal injury in a rat model, even when administered 2 hours after reperfusion. We have recently found that mice genetically engineered to not express ICAM-1 are also protected against ischemic acute renal failure. The research plan described in this proposal will extend these observations and allow me to work with Joseph V. Bonventre, M.D. Ph.D., a respected researcher in the pathophysiology of acute renal failure as well as experts in molecular biology, immunology and adhesion receptors, and signal transduction. I propose that inflammatory mediators are increased following renal ischemia and reperfusion. The mediators increase ICAM-1 expression especially in the outer medulla and facilitate leukocyte-endothelial interactions, medullary obstruction and ongoing ischemia. Increased ICAM- 1 expression may result from cytokine-mediated increases in stress activated protein kinase activity with phosphorylation of c-Jun and increased transcription of the ICAM-1 gene. Increases in circulating cytokine levels and systemic neutrophil activation may also be responsible for myocardial dysfunction following renal ischemia and renal dysfunction in sepsis. The following specific aims will explore several aspects of this hypothesis. I will: A.) Investigate ICAM-l expression following renal ischemia and reperfusion and determine the functional and histological consequences of renal ischemia in ICAM-1 deficient mice. B.) Evaluate the importance of leukocytes, platelets and hemodynamic alterations in the protection against ischemic injury seen with anti-ICAM- 1 antibody. The hypothesis that following renal ischemia/reperfusion, neutrophils accumulate largely in the renal medulla and that anti-ICAM-1 mAb inhibits the accumulation will be tested using immunocytochemical techniques to localize neutrophils. C.) Investigate the regulation of inflammatory cytokines following renal ischemia and reperfusion. Because inflammatory cytokines may be crucial in ICAM-l expression, I will investigate the effects of renal ischemia and reperfusion on serum levels of IL-1 and TNF-alpha. The contributions of platelet activating factor and nitric oxide to ICAM-1 expression and ischemic injury will also be evaluated. D.) Explore the hypothesis that ICAM-1 expression is regulated by stress- activated protein kinases and/or insulin like growth factor-1. E.) Evaluate the role of ICAM-1 expression and neutrophils in multi-organ dysfunction associated with acute renal ischemia and sepsis.